Recently, display apparatuses, such as liquid crystal displays and plasma displays, have been developed to be slimmed down. Also, display apparatuses with a larger-size screen have been recently become widely used.
A large-size flat panel display apparatus can be used in, for example, a presentation made at a conference or made in a product introduction, or used as a display apparatus for a video game. In such uses, a target point (i.e., a position) on an image displayed on a display screen is pointed by an operating device such as a pointer so that an operation is conducted.
For example, Patent Document 1 (Japanese Unexamined Patent Publication No. 2007-66080 (Tokukai 2007-66080, publication date: Mar. 15, 2007)) discloses an art for detecting coordinates of a pointed point on a display screen. In the art, (i) light emitting devices provided on front and rear surfaces of a pointer are driven based on respective different blinking patterns, (ii) an image, including light-emitting areas on the front and rear surfaces of the pointer, is captured by cameras provided on either side of the display screen, respectively, and (iii) directions (angles) in which the light-emitting areas exist and distances between the cameras and the light-emitting areas, respectively, are subjected to an arithmetical operation and are analyzed based on the trigonometry so that the coordinates of the pointed point on a display screen is detected.
Furthermore, Patent Document 2 (Japanese Unexamined Patent Publication No. 2007-83024 (Tokukai 2007-83024, publication date: Apr. 5, 2007)) discloses a system that detects coordinates of a position on a display screen. In the system, (i) a module with an LED that emits infrared light is provided in the vicinity of a display screen, for example, at an upper part or a lower part on a display apparatus, (ii) an image of the LED is captured by use of a filter that allows only infrared light to pass through and an image sensing device such as a CMOS sensor or a CCD image sensor, which filter and image sensing device are provided in a controller, and (iii) the coordinates of a position on the display screen are detected based on a positional change of the LED in the data of the image thus captured.
According to the conventional arts, unfortunately, a position pointed by the operating device may not be properly detected in a case where the operating device is positioned close to the display apparatus.
That is, according to the art disclosed in Patent Document 1, the display apparatus has, on either side of its display screen, the cameras for capturing an image including the light-emitting areas that are provided on the front and rear surfaces of the pointer (an operating device). As such, the positions of the light-emitting areas can be outside a range in which the camera can capture an image, in a case where the pointer is positioned close to the display screen.
As for the art disclosed in Patent Document 2, the LED module, provided at the upper or lower part on the display screen of the display apparatus, emits infrared light and the infrared light is captured by the image sensing device in the controller (an operating device). As in the case of Patent Document 1, the LED module can be outside a range in which the image sensing device can capture an image, in a case where the controller is positioned close to the display screen.
FIGS. 18(a), 18(b), 19(a), and 19(b) are explanatory views each illustrating a relation, in the case of the same arrangement as that disclosed in Paten Document 2, between (i) a distance between an operating device 101 and a display apparatus 102, and (ii) a range in which a position that is pointed by the operating device 101 can be detected.
In a case where the display apparatus 102 and the operating device 101 are away enough from each other as illustrated in FIGS. 18(a) and 18(b), it is possible to detect a position that is pointed by the operating device 101. This is because an LED module 103 is within a range in which an image sensing device in the operating device 101 can capture an image, irrespective of a position, on a display screen, pointed by the operating device 101.
In contrast, in a case where the display apparatus 102 and the operating device 101 are positioned close to each other as illustrated in FIGS. 19(a) and 19(b), the LED module 103 cannot be within the range in which the image sensing device can an image, depending on a position pointed by the operating device 101. In this case, it is impossible to detect the position pointed by the operating device 101.